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An anonymous reader writes to mention Nature is reporting that scientists have discovered a much more efficient way to use silicon to convert heat into electricity. This offers the possibility of many different applications including possibly charging your portable electronics just by wearing them close to your skin. "The concept of converting waste heat into electricity isn't exactly new, but it never really materialized due to efficiency hurdles. Now, scientists from the U.S. Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley think they may have found a key [to] increase the conversion efficiency by a factor of 100."

So now we have sperm powered nano-bots, and body heat powered gadgets, next thing you know it we will be running Human powered factories, data-centers.... and some punk-ass Rasta group with some Jaaaa trying to stop this...... Do not forget freakish spoon bending kids...

Now I have the ideal excuse to have Kathleen Turner's number on speed dial!

Unfortunately this tech comes 25 years too late. However, don't lose that number. It might still be useful for power generation using pre-petroleum technology (see:http://en.wikipedia.org/wiki/Whale_oil).

Think bigger.
Put these and some batteries near your brakes or under the hood of your car. Line the Shuttle with them, attach them to the boosters that get jettisoned. Tape them to politicians so all the hot air charges them.

Can I get this sucker to cool my CPU? Hotter, more power, faster the fan spins. I bet it draws down the heat when it extracts energy (required by laws of thermodynamics) and equalizing the heat between the CPU and surrounding air should provide power rather than take it. Really hot here, not hot here... that screams power.

Right, I'm not a scientist, but TFA talks about all sorts of fantastic things (e.g. charging your iPod with body heat) that aren't mentioned in the Abstract of the cited piece in Nature. While the article does quote one of the authors for such claims, what the Nature article Abstract (I'm not paying $ to read stuff online) alludes to is improving the efficiency of potential co-generation from sources of waste heat from combustion--power plants, car engines, etc. Besides, if it's cold enough out that I'm wearing a winter coat, do I really want to shove a heat sucking iPod down my pants? Not really. But sticking it against my car's engine? Sure.

Also TFA mentions "...the discovery will depend on whether these rough nanowires will be efficient enough to make commercial sense." So yeah, I don't see it (soon) being any more energy efficient to manufacture heat converting nanowires for my iPod Nano than it would be to say, construct a battery. But maybe they have something that could better convert a massive heat gradient into electrical energy cheaper for the purposes of co-generation. Who knows, maybe even cut down on heat pollution.

Note that this of course does also need a temperature gradient to work. This is no magic electricity creating cooling device.

Maybe you weren't aware, but the human body runs at a significantly higher temperature than the world around it. You'd have a hard time finding a place that that temperature gradient didn't exist. All this means is there has to be a large air-access radiating surface. No more phones the size of a stick of gum, since your hand would cover the cold spot. We don't need a magic cold c

...huddling before a fire, desperately trying to stay warm as their PDAs, cell phones, wireless earphones, etc. suck the little remaining heat from their bodies.
wait a minute, by the time this tech becomes widespread that might be me.

they talk about waste heat from steam turbines and car exhaust... and human bodies

is the sun's heat not enough to generate a substantial amount of energy? what would encasing one of these in a sealed dark glass box at lower latitudes do... or even inside of a hot car for that matter

Human body thermal output is about 120 watts on average, skin surface area is 2 m^2, so a 50-cm^2 cell phone body can intercept 0.6 watts of body heat. BUT, the laws of thermodynamics place a limit on how much of that heat can be converted into useful work to charge the batteries in the phone. That limit depends on the temperature of the heat source and sink.

Suppose one side of the phone is in contact with your skin at 32 C (305 Kelvin), and the other side is in contact with room-temperature air at 27 C (300 K). (In practice, the temperature difference will be smaller, because the air near your body will be warmed above room temp.) The maximum efficiency one could get from these thermodynamic efficiency is (305-300)/300 = 1.7%.

SO, the most energy we could possibly get out of this generation system is 0.6 * 1.7% = 10 milliwatts. My iPhone's battery holds about 2400 mW-hours of juice, so if I installed this charging system and held it against my skin 24/7, it would take about 10 days to charge in the theoretical best case... and in practice, much longer than that.

This idea's dead in the water at the basic physics stage, before we even get to the engineering considerations.

You put a lot of thought into that message, but it is negated by just RTFA which says that the potential applications include "...personal power-jackets that could use heat from the human body to recharge cell-phones...". They aren't talking about the cell phone itself drawing the power, but potentially the entire inner surface of a piece of clothing (which would also have the entire outer surface of the piece of clothing as the cooling surface for differential).

You are using the wrong denominator, (T_cold), in your calculation, although it hardly matters in this case because the temperature difference is so small. The formula for maximum theoretical efficiency is:

the human body is roughly at 310 kelvin while the rest of the room is typically much cooler than this. given a good way to conduct heat from one end to the other, the temp difference could be on the order of 15 degrees not 5 making it about 5% still not that much but probaly good enough for a wrist watch or a pocket calculator. then again, if there was a way for the cell phone not to be using full power constantly, there's no reason why you couldn't use the extra power to charge a Ni/Cd battery and use th

SO, the most energy we could possibly get out of this generation system is 0.6 * 1.7% = 10 milliwatts...
This idea's dead in the water at the basic physics stage, before we even get to the engineering considerations.

Actually, 10mW is loads. You're not going to charge batteries off that or run a GSM phone, but it's more than ample for powering things like wristwatches, calculators or medical sensors; and with appropriate design, there's no reason why you couldn't build a PDA that worked at that kind of po

You did not read the article, did you? Of course you didn't, this is slashdot!The article is talking about using the technology in the clothes and using the energy from that to power a cellphone. This would give you a lot more surface. And I don't know where you live, but "room temperature" here is not so tropical. So the theoretical maximum according to your calculation would be more like ((305-295)/295) * 120 = about 4 watts. Not a lot, but my telephone charger can provide about 2.2 watts and my battery i

So crank up the air conditioner and make the room cooler. Or just use Peltier elements to drain heat from the cold end of the generator. Coming to think of it, you could simply have a closed compartment, use Peltier elements to move heat from one side to the other, and run the generator - and power the Peltiers - from the resulting temperature gradient forever and ever.

What if instead of charging a cell phone through body heat, a battery was charged through a larger heat source. One could run pipes through their driveway (before it was poured obviously) that water is pumped through. That's an average of 57 square meters with an average daily insolation that is between 3 and 8 kW/m^2/day. During the day the driveway heats up considerably, which could then heat up a water tank, say a 50 gallon tank in your garage. The water could be used with this device to generate electri

I dunno where the heck you live but 27C is NOT room temp. "Room temp" is 20-22C. If my house was 27C year round I would not be able to wear pants!Assuming a more *NORMAL* room temp of 21C, the updated calculation is (305-294)/294 = 3.7%, or 21.76 milliwatts.

That is 4.5 days to charge fully from 0.

And you're also forgetting the point of this is not to take a dead battery from 0% to 100%, it is to MAINTAIN your current battery. As such I think this system could theoretically easily make it so you would rarely

In my house the other day room temperature was about 42, this was not the first time this year that this has happened, nor will it be the last. Room temperatures of the high 20's during summer(air conditioning not withstanding) are far from unusual here.

The effect has been known for a century... don't need to worry about classification!

Actually, at least here in the US, you probably should still worry about it being classified information.

For example, various historians have mentioned that the Rosenbergs were executed for giving "secrets" to the Russians that apparently were available in a number of college-level physics textbooks at the time.

Decades later (but still a few decades before today), I did an end-of-chapter exercise in a physics text that was something like: Using equations E and F from this chapter, and table T in appendix A, calculate the critical masses of the following isotopes.... There was an asterisk at the end, and the footnote said that telling any of the answers to a non-citizen was a felony under US law and listing the possible penalties (which included execution).

The US government's security agencies don't consider previous publication in school textbooks to be a restriction on their right to classify information.

For another example, google for RSA encryption. I have one of those t-shirts that has the 4-line perl implementation of RSA, and on the back "Warning: This t-shirt is a munition" plus a reference to the appropriate regulation. I never had the nerve to wear it to the airport on an international flight, though I did wear it to a number of techie meeting where there were non-citizens. I kept wishing someone would get arrested for wearing one, since the trial could have been entertaining. But I suppose now they wouldn't bother with a trial; you'd just disappear to an undisclosed location in an unstated country for a few years and then dropped off on a hillside in Macedonia when they're done with you.

Well, that's technical advance for you! I'll have to find that code. I expect it'll look like pure line noise. Also, I was being a bit generous with my original "4-line" description, since I counted the first #!/usr/bin/perl line, and that's not really what you could call perl code. Others only count it as three lines.

I did like the "-export-a-crypto-system-sig" comment in the original. Like many perl geeks, I have used it as a sig off

My dad was an engineer for a Naval submarine shipyard. He told me that thermoelectric panels attached to the inside of the hull cooled the submarine silently when a voltage was applied.Hope that wasn't classified or anything - but then Dad passed away a while back.

Let's just say I doubt it. Especially if it was "a while back". Won't say why, but trust me.

Anyway, the sea is an awesome heat sink - especially if you go down a bit in the right oceans. Just put your soda can on any seawater pipe. It's not th

Anyway, the sea is an awesome heat sink - especially if you go down a bit in the right oceans. Just put your soda can on any seawater pipe. It's not that hard to cool a submarine conventionally (with seawater as the heat sink instead of air).

The problem with this is that you don't want to conduct heat into the surrounding seawater. It leaves an easily detectable heat plume.

In fact, you want to heat the interior of the sub relative to the surrounding sea. So you make the hot side of the thermoelectric pan

Secondly, think about it. Everything in the sub from the bodies to the machinery makes heat. It has to be transferred out and the only place it can go is into the sea. The only question (and it's not a question, I know how it is done, or was, anyway) is how.

Is this effect reversible? Could it be turned into a super-efficient Peltier module?

It ought to be.

The problem with Peltier cells is the conduction of heat across the cell by means other than the charge carriers that perform the heat pumping/thermoelectric generation. This breakthrough is a drastic reduction in heat conduction. So it ought to be applicable to both heat pumping and generation. In fact the efficient thermogenerator ought to be an efficient heat pump as well.

You are always moving. Most likely the phone is in your pocket moving with you.

Have you seen those ever lasting flashlights. Which use a magnet, a coil and a capacitor. The same concept could be used here. It might not keep the phone charged for heavy users but it could be a nice supplement to the charger.

Maybe if they really got creative they could reuse the coil and magnet as the vibrator.OH and I didn't read the article. These are both interesting idea's but how much power can we really extract.

There's nothing about changing heat into electricity that violates the laws of thermodynamics.

But some of the hype in TFA DOES violate the laws of thermodynamics - exceeding the carnot cycle limit, sometimes by several orders of magnitude.

One of the other responses, for instance, calculates the power available from skin heat to a normal-sized cellphone at 10 mW. And the whole POINT of "waste heat" in a power plant is to dump it to ambient without restrictions that would raise the dump temperature and thus

How about using these in a water-heater sized device in your home. With a isotope heat source at the bottom, a coil lined with these strings, filled with some kind of heat transferring liquid (say, water). You could put one of these in every home and without any moving parts (as in a traditional thermonuclear generator with giant turbines) it would be very reliable.

I've seen this suggestion any number of times, often with snide comments about how engineers have missed something obvious. This usually causes some engineer to simply mention that there's a better way. No matter how your water heater is powered, it's always more efficient to add insulation to the water heater, and use the fuel that you save to directly power an electrical generator. This skips the stage of extracting power from the water heater's heat loss, and can thus extract more electricity from the fuel (or use less fuel to generate the same electricity).

Unfortunately for such schemes, it's only practical to extract energy from a heat gradient if the heat gradient is going to be there anyway. Then, if the extra weight isn't a problem, you might be able to use some of the heat you're losing to produce a small amount of electricity "for free" (i.e., at no additional fuel cost).

I guess I confused you by using "water heater" and "sized" next to each other. How about "washing machine sized" or "garbage can sized" instead. I'm not suggesting a water heater (or a washing machine, or a garbage can, just to be clear) I'm suggesting a closed-loop thermonuclear electric generator that likely wouldn't need to be too big to put in your garage.

Oh, sure, that works fine. It's how a lot of the long-lived space probes have been powered. In the inner solar system, solar cells are more practical, but as you pass Jupiter and Saturn, they deliver less and less power, so a chunk of radium or other radioisotopes works a lot better.

But I'm a bit dubious about the thought of a small nuclear power plant in the basements of my neighbors' homes...

"For longest time, I wouldn't belive it...and then I saw the fields with my own eyes. Watch them liquefy the dead, so they could be fed intravenously to the living. And standing there, facing the pure horrifying precision, I came to realize the obviousness of the truth. What is The Matrix? Control.
"The Matrix is a computer generated dream world, built to keep us under control in order to change a human being into this."
Morpheus holds up a battery to Neo
Neo begins to panic.

We have guests over, and their 20-something daughter seems to have a mobile glued to her ear. I was wondering if it had a nuclear powerplant or something keeping it going. Immediately struck me that it would great if the phone could somehow be powered by body heat.

"[Scientists] may have found a key increase the conversion efficiency by a factor of 100."
Let me guess, this is involves some form of fusion.. and the machines have found all the energy they will ever need.
This happened in a dream once, that I was so sure was real..

There are various research organizations (IMEC Belgium) looking into how to use the body's energy to power implantable devices (defib's, pacemakers, etc.) rather than batteries. They are looking at thermal, chemical, kinetic methods. The concept is birth to grave implantables that can also flex as the body grows and ages. They will be successful at some point. So it's a matter of developing these scavenging techniques, along with ultra low power semiconductors that will provide a foothold into the market.